The research proposed is designed to clarify further the nature of hormonally induced biochemical changes in the endometrium which enable the blastocyst or an analogous artificial stimulus to induce the process of decidualization and also to clarify the nature of the stimulatory, induction process itself. In order to accomplish these general objectives we propose to conduct experiments to determine the following: 1) the influence of estradiol and progesterone on the levels of maximally stimulated adenylate cyclase activity, protein kinase activity, membrane bound and soluble phospholipase activities, and on arachidonate conversion to prostanoids; 2) the hormonal priming prerequisites for the induction of decidualization by arachidonate; 3) whether activators of phospholipases will induce decidualization and, if so, what the priming prerequisites are; 4) whether inhibitors of phospholipases will prevent oil-induced decidualization; 5) whether intraluminal oil injection into primed uterine horns in vivo leads to the release of products of lecithin and phosphatidylinositol hydrolysis, including arachidonate; 6) whether the levels of prostaglandin endoperoxides are increased by intraluminal oil injection and also whether their levels are increased by priming when arachidonate is used as an exogenous precursor; 7) which of the above changes occur in epithelial and which occur in stromal cells of the endometrium, utilizing enzymic and mechanical methods to separate cell types and immunohistologic techniques to localize biochemical modulators. Most experiments will involve ovariectomized, hormonally treated mice but some will be done with mice bearing natural blastocysts for comparison with the artificial model system. This research will help to explain how the fertilized ovum induces changes in the biochemical functions of the adjacent uterine endometrium, changes which lead to the formation of the deciduoma. A better understanding of this process could be valuable in the development of treatments for certain types of habitual abortion and contraceptive methods based on interference with implantation.